1. Field of the Invention
The invention relates to synthetic chemical compositions that are useful for modulation of Toll-Like Receptor (TLR)-mediated immune responses. In particular, the invention relates to agonists of Toll-Like Receptor 9 (TLR9) that generate unique cytokine and chemokine profiles.
2. Summary of the Related Art
Toll-like receptors (TLRs) are present on many cells of the immune system and have been shown to be involved in the innate immune response (Hornung, V. et al., (2002) J. Immunol. 168:4531-4537). In vertebrates, this family consists of eleven proteins called TLR1 to TLR11 that are known to recognize pathogen associated molecular patterns from bacteria, fungi, parasites, and viruses (Poltorak, a. et al. (1998) Science 282:2085-2088; Underhill, D. M., et al. (1999) Nature 401:811-815; Hayashi, F. et. al (2001) Nature 410:1099-1103; Zhang, D. et al. (2004) Science 303:1522-1526; Meier, A. et al. (2003) Cell. Microbiol. 5:561-570; Campos, M. A. et al. (2001) J. Immunol. 167: 416-423; Hoebe, K. et al. (2003) Nature 424: 743-748; Lund, J. (2003) J. Exp. Med. 198:513-520; Heil, F. et al. (2004) Science 303:1526-1529; Diebold, S. S., et al. (2004) Science 303:1529-1531; Hornung, V. et al. (2004) J. Immunol. 173:5935-5943).
TLRs are a key means by which vertebrates recognize and mount an immune response to foreign molecules and also provide a means by which the innate and adaptive immune responses are linked (Akira, S. et al. (2001) Nature Immunol. 2:675-680; Medzhitov, R. (2001) Nature Rev. Immunol. 1: 135-145). Some TLRs are located on the cell surface to detect and initiate a response to extracellular pathogens and other TLRs are located inside the cell to detect and initiate a response to intracellular pathogens.
TLR9 is known to recognize unmethylated CpG motifs in bacterial DNA and in synthetic oligonucleotides. (Hemmi, H. et al. (2000) Nature 408:740-745). Other modifications of CpG-containing phosphorothioate oligonucleotides can also affect their ability to act as modulators of immune response through TLR9 (see, e.g., Zhao et al., Biochem. Pharmacol. (1996) 51:173-182; Zhao et al. (1996) Biochem Pharmacol. 52:1537-1544; Zhao et al. (1997) Antisense Nucleic Acid Drug Dev. 7:495-502; Zhao et al (1999) Bioorg. Med. Chem. Lett. 9:3453-3458; Zhao et al. (2000) Bioorg. Med. Chem. Lett. 10:1051-1054; Yu, D. et al. (2000) Bioorg. Med. Chem. Lett. 10:2585-2588; Yu, D. et al. (2001) Bioorg. Med. Chem. Lett. 11:2263-2267; and Kandimalla, E. et al. (2001) Bioorg. Med. Chem. 9:807-813). Naturally occurring agonists of TLR9 have been shown to produce anti-tumor activity (e.g. tumor growth and angiogenesis) resulting in an effective anti-cancer response (e.g. anti-leukemia) (Smith, J. B. and Wickstrom, E. (1998) J. Natl. Cancer Inst. 90:1146-1154). In addition, TLR9 agonists have been shown to work synergistically with other known anti-tumor compounds (e.g. cetuximab, irinotecan) (Vincenzo, D., et al. (2006) Clin. Cancer Res. 12(2):577-583).
Certain TLR9 agonists are comprised of 3′-3′ linked DNA structures containing a core CpR dinucleotide, wherein the R is a modified guanosine (U.S. Pat. No. 7,276,489). In addition, specific chemical modifications have allowed the preparation of specific oligonucleotide analogs that generate distinct modulations of the immune response. In particular, structure activity relationship studies have allowed identification of synthetic motifs and novel DNA-based compounds that generate specific modulations of the immune response and these modulations are distinct from those generated by unmethylated CpG dinucleotides. (Kandimalla, E. et al. (2005) Proc. Natl. Acad. Sci. USA 102:6925-6930. Kandimalla, E. et al. (2003) Proc. Nat. Acad. Sci. USA 100:14303-14308; Cong, Y. et al. (2003) Biochem Biophys Res. Commun. 310:1133-1139; Kandimalla, E. et al. (2003) Biochem. Biophys. Res. Commun. 306:948-953; Kandimalla, E. et al. (2003) Nucleic Acids Res. 31:2393-2400; Yu, D. et al. (2003) Bioorg. Med. Chem. 11:459-464; Bhagat, L. et al. (2003) Biochem. Biophys. Res. Commun. 300:853-861; Yu, D. et al. (2002) Nucleic Acids Res. 30:4460-4469; Yu, D. et al. (2002) J. Med. Chem. 45:4540-4548. Yu, D. et al. (2002) Biochem. Biophys. Res. Commun. 297:83-90; Kandimalla. E. et al. (2002) Bioconjug. Chem. 13:966-974; Yu, D. et al. (2002) Nucleic Acids Res. 30:1613-1619; Yu, D. et al. (2001) Bioorg. Med. Chem. 9:2803-2808; Yu, D. et al. (2001) Bioorg. Med. Chem. Lett. 11:2263-2267; Kandimalla, E. et al. (2001) Bioorg. Med. Chem. 9:807-813; Yu, D. et al. (2000) Bioorg. Med. Chem. Lett. 10:2585-2588; Putta, M. et al. (2006) Nucleic Acids Res. 34:3231-3238).
The inventors have surprisingly discovered that uniquely modifying the sequence flanking the core CpR dinucleotide, the linkages between nucleotides or the linkers connecting the oligonucleotides produces novel agonists of TLR9 that generate distinct in vitro and in vivo cytokine and chemokine profiles. This ability to “custom-tune” the cytokine and chemokine response to a CpR containing oligonucleotide provides the ability to prevent and/or treat various disease conditions in a disease-specific and even a patient-specific manner. Thus, there is a need for new oligonucleotide analog compounds to provide such custom-tuned responses.